Ultrastructure of calcified muscle fibres at the implantation site of demineralized bone matrix gelatin.

To clarify the mechanism of calcification during new bone formation induced by demineralized bone matrix gelatin (BMG), BMG was implanted into the skeletal muscle of Sprague-Dawley (SD) rats and histological changes were examined 1,2,3,5,7 and 10 days later. From day 2 after implantation, calcification was observed in muscle fibres near the implanted BMG. Calcification of the BMG ('acellular mineral deposition') was first seen on day 3 and in both, calcification increased. The calcification of muscle fibre was first seen in the sarcoplasmic reticulum (SR) and then in mitochondria or lipid droplet-like structures of satellite cells. The muscle mineral deposition occurred without osteogenic cells and matrix vesicles in the same way as 'acellular mineral deposition'.